Prior to 1961, a unit of atomic weight was based on 1/16th (0.0625) of the weight of an oxygen atom. After this point, the standard was changed to be 1/12th the weight of a carbon-12 atom in its ground state. A carbon-12 atom is assigned 12 atomic mass units. The unit is dime...
they are found in. Protons have a mass of 1.673x10^-24 grams and neutrons have a mass of 1.675x10^-24 grams. These are very small numbers so their weights are often given in their atomic mass units (amu), which is 1.0073amu and 1.0087amu respectively. An amu is 1.66054x10^-24 grams...